Galactic cosmic rays are generally assumed to be accelerated in supernovae and their remnants.
The acceleration of the particles is attributed to their repeatedly interaction with the supernova remnant shock front. Model calculations have shown that a significant fraction of the supernova explosion energy can be converted to energy of cosmic rays. The feedback of this large energy transfer on the dynamical evolution and its impact on the age estimates of supernova remnants is addressed. True ages might be significantly lower than the standard Sedov ages. The impact is described by a quantitative model, which is tested on RX J0852.0-4622 (Vela Jr). Independent of this test conclusions are drawn about the evolution and lifetime of shell-type X-ray synchrotron sources and TeV gamma-ray sources associated with supernova remnants.